title: The use of epithelial membrane antigen and silver-stained nucleolar organizer regions testing in the differential diagnosis of mesothelioma from benign reactive mesothelioses.
abstract: BACKGROUND
  The accurate diagnosis of pleural lesions obtained from small closed biopsy is difficult. As yet there is no single reliable test to distinguish between malignant and benign mesothelial tissue.
  
  
  METHODS
  Immunostaining of epithelial membrane antigen (EMA) and the quantitation of silver stained nucleolar organizer regions (AgNORs) each were applied to benign and malignant histologic sections of pleural and peritoneal biopsies. The usefulness of these stains was tested both individually and in combination in the diagnosis of epithelial malignant mesothelioma.
  
  
  RESULTS
  One hundred and three of the 141 malignant lesions (73%) were immunoreactive for EMA but only 3 of the 73 benign lesions (4%) reacted equivocally, and none positively. The average count of AgNORs/cell in malignant lesions (n = 80) was elevated compared with benign cases (n = 26), but a significant overlap was exhibited in the AgNOR count and this form of analysis was considered to be of little value in distinguishing benign from malignant mesothelial processes. Much less overlap was observed when the average AgNOR area was measured. By using the maximum benign AgNOR area of 0.6677 microm2 as the upper threshold, 51 cases (63.8%) were identified as malignant; the test demonstrated 100% specificity and 63.8% sensitivity. By combining the EMA and AgNOR results, 76 of 80 of the malignant mesothelioma cases (95%) tested positive for at least 1 of the tests with no false-positive results identified.
  
  
  CONCLUSIONS
  This study confirms the usefulness of EMA in diagnosing malignant and benign mesothelial lesions, and demonstrates the enhanced diagnostic value of combining EMA immunoreaction with the average area of AgNOR per cell, thereby increasing sensitivity in the diagnosis of epithelial malignant mesothelioma.
authors.affiliation: Western Australian Centre for Pathology & Medical Research, Queen Elizabeth II Medical Centre, Nedlands.
authors.forename: K D
authors.initials: KD
authors.lastname: Wolanski
authors.forename: D
authors.initials: D
authors.lastname: Whitaker
authors.forename: K B
authors.initials: KB
authors.lastname: Shilkin
authors.forename: D W
authors.initials: DW
authors.lastname: Henderson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D004848:Epithelium / Q000473:pathology; D005260:Female; D006801:Humans; D006965:Hyperplasia; D007150:Immunohistochemistry; D008297:Male; D008654:Mesothelioma / Q000737:chemistry / Q000175:diagnosis* / Q000473:pathology; D008875:Middle Aged; D018396:Mucin-1 / Q000032:analysis*; D009697:Nucleolus Organizer Region / Q000473:pathology*; D010534:Peritoneal Neoplasms / Q000737:chemistry / Q000175:diagnosis / Q000473:pathology; D010995:Pleural Diseases / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology; D010997:Pleural Neoplasms / Q000737:chemistry / Q000175:diagnosis / Q000473:pathology; D012680:Sensitivity and Specificity; D016622:Silver Staining
chemical_list: D018396:Mucin-1